@graffy/common/esm/coding/base64.js

Common libraries that used by various Graffy modules.

import alpha from './alphabet';

function getByte(view, offset) {
  return offset < view.byteLength ? view.getUint8(offset) : 0;
}

function getChar(string, offset) {
  return offset < string.length ? alpha.indexOf(string[offset]) : 0;
}

export function encode(u8Arr) {
  var buffer = u8Arr.buffer,
      byteOffset = u8Arr.byteOffset,
      byteLength = u8Arr.byteLength;
  var view = new DataView(buffer, byteOffset, byteLength);
  var str = '';

  for (var i = 0; i < view.byteLength; i += 3) {
    var value = (getByte(view, i) << 16) + (getByte(view, i + 1) << 8) + getByte(view, i + 2);
    var gstr = '';

    for (var j = 0; j < 4; j++) {
      gstr = alpha[value & 0x3f] + gstr;
      value = value >> 6 | 0;
    }

    str += gstr;
  }

  return str.substr(0, Math.ceil(view.byteLength * 4 / 3));
}
export function decode(string, start) {
  if (start === void 0) {
    start = 0;
  }

  var buffer = new ArrayBuffer(Math.floor((string.length - start) * 3 / 4));
  var view = new DataView(buffer);

  for (var i = start; i < string.length; i += 4) {
    var value = (getChar(string, i) << 18) + (getChar(string, i + 1) << 12) + (getChar(string, i + 2) << 6) + getChar(string, i + 3);

    for (var j = i * 3 / 4 + 2; j >= i * 3 / 4; j--) {
      if (j < view.byteLength) view.setUint8(j, value & 0xff);
      value = value >> 8 | 0;
    }
  }

  return new Uint8Array(buffer);
}